What does Jesus mean when He says that not everyone who calls Him Lord Lord will enter into the kingdom of heaven

Jesus is passing sentence here upon those who do not bear fruit for God's eternal kingdom (CP V20-27). Jesus makes it quite clear here that no one merely professing to be a Christian will be saved - only those who hear God's word and do it will enter into the kingdom of heaven (CP Psa 119:9; Pr 4:4; Ro 2:13; Jas 1:22-25; Rev 1:3). These scriptures all teach the same thing: the only way to heaven is by doing the work of God's word - no one can be saved by merely believing in Jesus (CP Jas 2:14-26). Demons also believe in Jesus, but they are not going to heaven. This is a warning for believers, not unbelievers. Those who profess faith in Christ must conform strictly to His word. There can be no compromise - believers not doing the work of God's word for Christ, are doing the work of the devil against Christ (CP Mt 12:30). Professing Christians who are not bearing fruit for God's eternal kingdom will not be part of the kingdom, and it is folly for them to think they will.